Accepting Sanyasa

Vasudeva returned home from the gurukula at the age of eight,
determined to become an ascetic. He realized that this was the
only way he could propagate the true philosophy enshrined in the
holy scriptures and establish the unrivalled and unequalled
supremacy of God. His parents were very distressed to hear this
since he was their only son. Vasudeva relieved them by promising
to wait until another son was born to them. When another baby
was born, vAsudeva sought and obtained his parents permission,
which was provided reluctantly.

achyuta prekSha tIrtha (some say that his name was achyuta
pragna), a great ascetic belonging to Advaita (non-dualistic)
school of Vedanta, had his maTha in the Ananteshvara shrine. He
was the spiritual leader of the community at that time and so
vAsudeva requested him to take him as his disciple.
achyutaprekSha, who was eagerly waiting for a worthy disciple
immediately agreed. Vasudeva was inducted into sanyAsa (monkhood)
with pUrNapragna as his Ashrama-nAma (name taken after one
becomes a monk)